The present invention relates to a freewheel hub for a bicycle.
Freewheel hubs have been disclosed in the prior art. For example, document DE 198 47 673 A1 shows a freewheel hub in which two coupling rings are each biased towards one another by means of a spring associated therewith. The disadvantage of this solution is that all components are arranged axially next to one another which leads to a relatively large axial length which is necessary for the freewheel arrangement. Also, the fact that both coupling rings are in each case formed with an external or peripheral tooth system for the transmission of torque with the sprocket arrangement or with the hub housing respectively makes for a significant installation space requirement, as these teeth must be sized to be sufficiently sturdy and long to guarantee reliable operation. Further, freewheel hubs of this design, in which at least one of the coupling rings is biased towards the other by means of a spring, have the disadvantage that they develop a relatively large amount of noise in the freewheel state, which is frequently perceived as annoying, particularly with freewheel hubs which are used in competitive sport or by ambitious and demanding amateur sportsmen.
A similar solution is also shown in each of the documents DE 197 31 451 A1 and DE 298 03 667 U1.
Document U.S. Pat. No. 5,676,227 shows a comparable solution in which only one of the coupling rings is biased towards the other coupling ring by means of a spring. However, with regard to the necessary installation space, this solution is comparable with the solutions in the prior art described above. This solution also develops significant noise in the freewheel state.
Document EP 2 422 996 A1 describes a freewheel hub in which an axially moving coupling ring, which is formed with the hub housing for the purpose of transmitting torque, is biased by means of magnetic forces towards a spur gear fitted to a sprocket carrier.
Finally, with regard to the technical background, reference is made to documents U.S. Pat. No. 5,964,332 and U.S. Pat. No. 5,493,799.